[PATCH] Teach DeadArgElimination not to eliminate return values of functions with 'returned' arguments

[Stephen Lin]

> But definitely, the information that the physical register containing
> the return value and argument are aliases of each other should not be
> lost, and code generation should not be forced to choose one or the

To pedantically self-correct myself...I realize "alias" is not
actually the right word for this, in retrospect. I mean that the two
are guaranteed hold the same value until invalidated (but they don't
refer to the same storage location, obviously.)

Stephen